Direct Hydrocarbon Indicators (DHIs) arise from contrasts in properties between either hydrocarbon- and water-saturated portions of a reservoir or a hydrocarbon-saturated reservoir and its encasing seal (FIG. 1). Current practices for ranking a potential hydrocarbon opportunity based on DHIs in seismic data involve a rather subjective procedure applied to previously-identified leads.
However, any given hydrocarbon occurrence can be manifested in seismic data by a variety of indicators, making it particularly difficult to qualitatively assess the myriad of possible responses from varied combinations of DHIs. Vast knowledge of the geologic setting, geologic history, and reservoir type is required before one can even hypothesize what individual DHIs and/or combination of DHIs should be present for a particular lead.
Currently, DHI analyses are used as a tool to lend confidence to a hypothesis of hydrocarbon presence for a given lead (Exploration Seismology, Sheriff and Geldart, Cambridge University Press, 2nd ed., pp 415-418 (1995)). However, additional quantitative work can be done regarding definition of DHIs and analysis of their geologic/geophysical meaning. It is generally recognized that the more that is known about various DHI indicators and their manifestation in different geologic settings, the more DHIs can be manipulated to aid in the identification of hydrocarbon opportunities. What is needed is a system that can utilize DHIs to their full potential by putting no limits or assumptions on the DHI analysis process. Instead of looking for a defined set of indicators that is qualitatively assessed to determine the presence of hydrocarbons in a given setting, which is the traditional method of DHI analysis, it may be more productive to let the DHIs, in whatever combination they may be manifested, guide the interpreter to hydrocarbon opportunities. The present invention satisfies this need.
Following is a brief summary of some previous published approaches for solving the same or a similar technical problem.
U.S. Pat. No. 6,587,791, “System and method for assigning exploration risk to seismic attributes” to Dablain et al., discloses a method for assessing the geologic risk for hydrocarbon presence and hydrocarbon accumulation size. Direct Hydrocarbon Indicators derived from seismic data are used to qualify the presence and accumulation size.
PCT Patent Publication WO2009142872, “Seismic Horizon Skeletonization” by Imhof et al., discloses an automatic method to extract a large number of horizons from a seismic dataset. Moreover, it discloses a broad pattern recognition workflow that partitions a dataset, analyzes the regions, and ranks them according to their potential of containing hydrocarbons.
PCT Patent Publication WO2009011735, “Geologic Features From Curvelet Based Seismic Attributes” by Neelamani and Converse, discloses a method for the computation of hydrocarbon indicators or texture attributes that may be used for the identification of subsurface features.
PCT Patent Publication WO2010056424, “Windowed Statistical Analysis for Anomaly Detection in Geophysical Datasets” by Kumaran et al., discloses a method of partitioning to identify geologic features from geophysical or attribute data using windowed principal component analysis.
PCT Publication No. WO2011149609, “System for Seismic Hydrocarbon System Analysis” by Imhof et al., discloses a method to detect and rank potential hydrocarbon opportunities using seismic data.
U.S. Pat. No. 5,440,525, “Seismic data hydrocarbon indicator” to Dey Sarkar et al., discloses a method for processing seismic data using conventional amplitude versus offset techniques to obtain AB cross plots on a trace-by-trace basis that are then utilized to generate a display that provides indications of the locations of hydrocarbons.
U.S. Pat. No. 5,453,958, “Method for locating hydrocarbon reservoirs” to Neff, discloses a method to produce a display that indicates the location of hydrocarbons based on a calculation of change in seismic amplitude divided by dip magnitude at individual grid points.
U.S. Pat. No. 6,092,025, “Hydrocarbon edge detection using seismic amplitude” to Neff, discloses a computer implemented method to produce a display that indicates the location of hydrocarbons based on a calculation of change in seismic amplitude divided by dip magnitude at individual grid points.
EP Patent No. 1,110,103, “Method of Seismic Signal Processing” to Meldahl et al., discloses a method of processing seismic data that extracts information along the spatial direction of a body of interest thereby producing directional seismic attributes.
U.S. Pat. No. 6,603,313, “Remote Reservoir Resistivity Mapping” to Srnka et al., discloses a method for surface estimation of reservoir properties using electromagnetic responses to produce inverted vertical and horizontal resistivity depth images.
U.S. Pat. No. 6,735,526, “Method of combining directional seismic attributes using a supervised learning approach” to Meldahl et al., discloses a method of combining directional seismic attributes using a supervised learning approach which may include extracting information along the spatial direction of a body of interest.
U.S. Pat. No. 7,266,041, “Multi-attribute background relative scanning of 3D geophysical datasets for locally anomalous data points” to Padgett, discloses a method for scanning geophysical data sets to find anomalous geophysical responses that can be related to the presence of hydrocarbon or water bearing strata.
U.S. Pat. No. 7,206,782, “Method for deriving a GrAZ seismic attribute file” to Padgett, discloses a method for deriving a GrAZ seismic attribute file that utilizes horizon vectors and attribute vectors to ascertain if changes are occurring in a direction towards a surface datum for a given time and depth range.
U.S. Pat. No. 7,453,767, “Method for deriving a 3D GRAZ seismic attribute file” to Padgett, discloses a method of determining and analyzing spatial changes in the earth's subsurface. The method obtains seismic attribute data and corresponding 3D dip and azimuth volumes as well as 3D reliability volumes to identify regions likely to be proximal to a seismic flat spot and/or hydrocarbon.
U.S. Pat. No. 7,453,766, “Method for deriving 3D output volumes using summation along flat spot dip vectors” to Padgett, discloses a method that is an adaptation of that disclosed in U.S. Pat. No. 7,453,767.
U.S. Pat. No. 7,463,552, “Method for deriving 3D output volumes using filters derived from flat spot direction vectors” to Padgett, discloses a method that is an adaptation of that disclosed in U.S. Pat. No. 7,453,767.
U.S. Pat. No. 7,697,373, “Method for deriving 3D output volumes using dip vector analysis” to Padgett, discloses a method that is an adaptation of that disclosed in U.S. Pat. No. 7,453,767.
Other references include the following.
Exploration Seismology by Sheriff and Geldart, Cambridge University Press, 2nd ed., pages 415-418 (1995) presents an overview of the mechanisms behind the generation of and manifestations of hydrocarbon indicators in seismic data.
Quantitative Seismology: Theory and Method” by Aki and Richards, W.H. Freeman and Co., 153 (1980) discloses a method to approximate reflection amplitude as a function of offset and elastic rock properties.
“A simplification of the Zoeppritz equations” by Shuey, Geophysics 50, 609-614 (1985) discloses a method of simplification of the Zoeppritz equations to approximate amplitude change as a function of offset.
“Weighted stacking for rock property estimation and detection of gas” by Smith and Gidlow, Geophysical Prospecting 35, 993-1014 (1987) presents a method using approximations of the Zoeppritz equations and derived rock properties to produce a fluid factor volume indicative of the presence of gas.